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Up to 22% Dips Detected in Starlight 1,500 LY Away

Courtesy of The Atlantic:

In the Northern hemisphere’s sky, hovering above the Milky Way, there are two constellations—Cygnus the swan, her wings outstretched in full flight, and Lyra, the harp that accompanied poetry in ancient Greece, from which we take our word “lyric.”

Between these constellations sits an unusual star, invisible to the naked eye, but visible to the Kepler Space Telescope, which stared at it for more than four years, beginning in 2009.

“We’d never seen anything like this star,” says Tabetha Boyajian, a postdoc at Yale. “It was really weird. We thought it might be bad data or movement on the spacecraft, but everything checked out.”

...

The light pattern suggests there is a big mess of matter circling the star, in tight formation. That would be expected if the star were young. When our solar system first formed, four and a half billion years ago, a messy disk of dust and debris surrounded the sun, before gravity organized it into planets, and rings of rock and ice.
But this unusual star isn’t young. If it were young, it would be surrounded by dust that would give off extra infrared light. There doesn’t seem to be an excess of infrared light around this star.
It appears to be mature.

I think it's safe to say a planet wouldn't block out so much light, no matter how big. As far as we know, this is a single-star system so there also isn't a second star orbiting around (or else we would see it!). So that leaves the question open to interpretation. A giant megastructure like a Dyson sphere might be a tempting answer, but I'm not sure I'd go that far just yet.

This is still a work-in-progress as of this writing, awaiting further investigation.

Note to Mods: If this doesn't fit in Life in Space, please feel free to move it to Astronomy. I wasn't sure where to post it, but I figured it would foster a more interesting discussion in Life in Space given the connotations.

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

I think we can assume it is not a problem with how the data was collected or processed.

No need to assume. The astronomers who published the study have confirmed as much. It isn't a problem with the data or a technical issue with the telescope. It seems pretty real.

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

Here's a page I helped to make about various Dyson swarm concepts, some more far-fetched than others.http://www.orionsarm.com/eg-article/4845fbe091a18
If this is a system containing light-collecting megastructures this might be the most momentous discovery to come out of Kepler.

I wonder if we have the technology at this point to make a definitive conclusion either way as far as natural vs. alien technology? I suppose once we take a closer look there could be something obvious to prove either hypothesis, but it may be that we just aren't yet capable of gathering enough info to be sure. I also wonder if the James Webb telescope will be able to gather more detailed info.

Here's a page I helped to make about various Dyson swarm concepts, some more far-fetched than others.http://www.orionsarm.com/eg-article/4845fbe091a18
If this is a system containing light-collecting megastructures this might be the most momentous discovery to come out of Kepler.

Very interesting, thanks! I'll have to give it a more thorough look later tonight.

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

None of the astronomical explanations for the star dimmings sound very convincing. The most favored one, comets driven inward by a passing star, seems to have problems of its own. Does it seem reasonable that comets would bunch up together, so as to cause some of the fairly rapid shifts in brightness reported, and that they could in any likely configuration diminish the star's light by 15 to 22 percent?

I've given this enough credence to write on it myself, but: The article is credible because it's clear that ETI as an explanation is one of the last places to go with this, and right now this is just something odd. It would take a lot of investigation and surprising results over a long time before the idea of it being an alien strycture would be seriously put for consideration. The most we could say at the moment is that right noiw the evidence at hand doesn't actually disprove ETI as a hypothesis.

I've used it, I've seen it around a lot as you say so I assumed it was standard usage licience. I did try to track down the author to credit it properly but had no luck. I can take it down right away if you want, or I'll credit it to you?

As far as I can tell, the light curve suggests objects distributed in a relatively tight group along a small section of orbit that has a period of about 700 days. Most of that time there's little activity in the light curve, except during the passage of these things.

I'd have to pull quotes directly from their report to defend this, but it seems pretty clear that the objects are only a tiny arc of a large orbit.

That's what they are going for next. If you read Phil's article, the team is applying for telescope time for further investigation, which is expected to take another 6-12 months until the results are published. Until then, the paper they just published seems pretty clear on what is being described, the lack of data notwithstanding.

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

As far as I can tell, the light curve suggests objects distributed in a relatively tight group along a small section of orbit that has a period of about 700 days. Most of that time there's little activity in the light curve, except during the passage of these things.

I'd have to pull quotes directly from their report to defend this, but it seems pretty clear that the objects are only a tiny arc of a large orbit.

Report here. No periodicity evident in the light dips from the current data .. see page #10: '4.4.1 Scenario independent constraints' ...

The lack of evidence for periodicity in the dips in the observed light-curve excludes orbital periods shorter than ∼ 1500 days, which thus constrains the location to lie beyond about 3 AU. This constraint could be broken if the clumps disperse within a single orbit ...

They go further in considering this, but there is no periodicity evident from the current data.

So, they then go on considering model dependent interpretations, and it appears that the cited 750 day 'periodicity' is scenario dependent. They invoke a giant impact within the planetary system model (Section 4.4.3). The conclusion is:

Two new issues arise with this scenario however. Firstly, if the period of the orbiting material is a few years, what is the origin of the two small dips seen in the first few hundred days, and why did they not repeat 750 days later? While Section 3 constrained the number of > 5% dips toward Kepler stars, it was not possible to determine the fraction of stars that exhibit 0.5% dips such as these.However, it is a concern that these could require the existence of anouter planetesimal belt, which may contradict the lack of infrared emission to this star. Perhaps more problematic is the probability that this star (of unknown age) should suffer such an event that occurs within a few-year window between the WISE observation and the end of the prime Kepler mission, and that the geometry of the system is such that material orbiting at ∼1.6 AU lie almost exactly between us and the star? Taking this few year window, the main sequence lifetime, and an optimistic estimate for the scale height of giant impact debris, and the number of Kepler stars observed, this suggests that every star would have to undergo 104 such impacts throughout its lifetime for us to be likely to witness one in the Kepler field. Thus, while this scenario is attractive because it is predictive, the periodicity argument may be inconsistent, and the probability of witnessing such an event may be very low (though of course hard to estimate).

Its a good, quite thorough analysis, and it ends up with the inevitable conclusion of 'more data needed'.

As far as I can tell, the light curve suggests objects distributed in a relatively tight group along a small section of orbit that has a period of about 700 days. Most of that time there's little activity in the light curve, except during the passage of these things.

I'd have to pull quotes directly from their report to defend this, but it seems pretty clear that the objects are only a tiny arc of a large orbit.

A Dyson sphere would be the end state of a long period of growth. With the desire to keep things close together as much as possible to limit lightspeed lag, transportation costs, travel time, etc, a civilization forming a Dyson sphere would look like a bunch of objects orbiting in close formation, maybe in multiple clumps in orbits with different periods, probably not in clean symmetrical shapes with sharp boundaries, probably varying with time, not emitting as much infrared as dust would, and possibly emitting it preferentially in a direction away from us.

So...yes, it would probably look much like these observations. And it's not straightforward to come up with a natural explanation.

As far as I can tell, the light curve suggests objects distributed in a relatively tight group... Most of that time there's little activity in the light curve, except during the passage of these things.

Right. So on day 793, a single object is apparently in the process of transiting. Apparently a very big object orbiting in front of that star! If I'm reading the graph right, from first dimming, it looks like it takes about 4 or 5 days for the object to reach 'peak obscuration'. It doesn't make sense, then, that the star would be back to full brighness in what looks like 2 days. Wha..? Phil mentions that, too. What model accomplishes that? I guess the object's orbit would have to be pretty eccentric, and it's diving away from us toward the star. So it accelerates as it ends its transit....

Right. So on day 793, a single object is apparently in the process of transiting. Apparently a very big object orbiting in front of that star! If I'm reading the graph right, from first dimming, it looks like it takes about 4 or 5 days for the object to reach 'peak obscuration'. It doesn't make sense, then, that the star would be back to full brighness in what looks like 2 days. Wha..? Phil mentions that, too. What model accomplishes that? I guess the object's orbit would have to be pretty eccentric, and it's diving away from us toward the star. So it accelerates as it ends its transit....

See Section 4.4.5 'A comet family?' (The eccentricity of a family of exo-comet fragments makes it all work out .. pending more data).

From the abstract:

By considering the observational constraints on dust clumps orbiting a normal main-sequence star, we conclude that the scenario most consistent with the data in hand is the passage of a family of exocomet fragments, all of which are associated with a single previous breakup event. We discuss the necessity of future observations to help interpret the system.

Where is the re-emitted IR needed for the highly pliable, mythical 'Dyson Sphere'? How can this be 'consistent with' a missing IR characteristic?

There's no missing IR. As Phil put it, "We know how much IR stars like KIC 8462852 give off, and we see just the right amount from it, no more." That means the transiting object must not be a big dust cloud from a big planetary collision, which would produce an IR excess.

There's no missing IR. As Phil put it, "We know how much IR stars like KIC 8462852 give off, and we see just the right amount from it, no more." That means the transiting object must not be a big dust cloud from a big planetary collision, which would produce an IR excess.

Comet debris .. read the report. There is no mention of the mythical 'Dyson Sphere' in the science report!

Have they ruled out the possibility that it is some internal process that we don't understand, that for whatever reason the star has become unstable?

I don't think the paper has addressed that. That said, I can't think of any internal processes that would cause the star to be so unstable as to dim by 15-22%. (Also, I believe it is a main sequence star.)

“Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

Ah, thanks. Yes, interesting paper! Near the end they state: "The light-curve expected for a typical [cometary] event then has a relatively fast ingress as the head of the comet passes in front of the star, but a slower egress as the tail passes," then they note, as I did, that it's just the opposite with the "D800" event.

Ah, thanks. Yes, interesting paper! Near the end they state: "The light-curve expected for a typical [cometary] event then has a relatively fast ingress as the head of the comet passes in front of the star, but a slower egress as the tail passes," then they note, as I did, that it's just the opposite with the "D800" event.

Yes ... and then, immediately following, they say:

Possible resolutions of this issue are that the D800 comet fragment received a large kickwith an orientation that sheared it out in such a way to form a “forward tail”. Such forward comet tails produced by the fragments being kicked toward the star have been studied in the literature,but require the tail to be large enough to overcome the effects ofradiation pressure (Sanchis-Ojeda et al. 2015). Alternatively, this event could be comprised of two dips superimposed to have the appearance of a forward tail. While several issues remain to be explored, of the scenarios considered we conclude that a cometaryorigin seems most consistent with the data to hand.

I'm surprised that some comets are thought to be able to block 22% of the light reaching us from the star.
My thoughts were multiple debris clusters from a collision between two planets in significantly different orbits. The results would have a range of different periods, and the clusters themselves might change significantly in shape over the course of an orbit, disguising the periodicity of the individual components. Main problem: where's the dust? If it's not dust doing the blocking, it seems like there must be a considerable mass of material that should be producing new dust through occasional collisions...